The present invention relates to an improved process for establishing ohmic contacts or studson thin films of metals or metal compounds such as, for example, nitrides. The problem of establishing ohmic contacts on thin films (the maximum thickness of which is a few tenths of micrometers) is generally solved by the localized desposition of metal or of a metal alloy such as gold or alloys of nickel and chromium, as is in fact well known. Among known processes, mention may be made of those requiring a relatively large number of intermediate layers or films between the thin film circuit and the metal stud. By way of example, solutions have been described utilizing intermediate layers of titanium and palladium. A simpler solution of establishing ohmic contacts on layers of tantalum nitride is disclosed in U.S. Pat. No. 3,793,175 granted to the same assignee.
The problem involved in the establishment of these contacts is relatively complex due to the mounting requirements of these circuits. It is in fact most frequently required that the interconnections of these circuits be established by thermocompression or by means of gold eutectic alloys. In specific cases, it is required that tin soldering should be possible.
The present invention affords a solution of this problem which is particularly interesting in the case of tantalum nitride thin film circuits. It permits, in fact, the reduction within a factor higher than 2 of the quantity of gold necessary for thermocompression interconnecting. It also permits an improvement in the yield of the thermocompression step and also an improvement in the ageing ratio.